Moon Rock

This is a fragment of the "Great Scott Rock", lunar
sample 15555 [direct link to 4.8 megabyte PDF], which that PDF notes is
"the largest and most intensively studied of the Apollo 15 rocks". NASA's Lunar Sample
Public Displays page has a "Complete List of Lunar Sample Displays" PDF
which lists this sample as 15555,767.

The Lunar
and Planetary Institute's atlas entry for 15555 [direct link to 1.2 meg
PDF] contains additional information on 15555. Although it notes that a ",776"
fragment was cut from 15555 for display purposes, there is no mention of a
",767" fragment, leading me to wonder whether there's a typographical error in
the JSC public displays PDF.

The LPI has a page with many
photos of the original 15555 sample, as well as photos of the various
sections into which 15555 was cut. (Unfortunately, there are no photos of
either 15555,767 or 15555,776 for comparison purposes.)